Pectin as a novel natural kinetic hydrate inhibitor, expected to be eco-friendly and sufficiently biodegradable, was studied in this paper. The novel crystal growth inhibition (CGI) and standard induction time methods were used to evaluate its effect as hydrate inhibitor. It could successfully inhibit methane hydrate formation at subcooling temperature up to 12.5 °C and dramatically slowed the hydrate crystal growth. The dosage of pectin decreased by 66% and effective time extended 10 times than typical kinetic inhibitor. Besides, its maximum growth rate was no more than 2.0%/h, which was far less than 5.5%/h of growth rate for PVCap at the same dosage. The most prominent feature was that it totally inhibited methane hydrate crystal rapid growth when hydrate crystalline occurred. Moreover, in terms of typical natural inhibitors, the inhibition activity of pectin increased 10.0-fold in induction time and 2.5-fold in subcooling temperature. The extraordinary inhibition activity is closely related to its hydrogen bonding interaction with water molecules and the hydrophilic structure. Finally, the biodegradability and economical efficiency of pectin were also taken into consideration. The results showed the biodegradability improved 75.0% and the cost reduced by more than 73.3% compared to typical commercial kinetic inhibitors.

Abstract-This paper investigates the compress-and-forward scheme for an uplink cloud radio access network (C-RAN) model, where multi-antenna base-stations (BSs) are connected to a cloudcomputing based central processor (CP) via capacity-limited fronthaul links. The BSs compress the received signals with Wyner-Ziv coding and send the representation bits to the CP; the CP performs the decoding of all the users' messages. Under this setup, this paper makes progress toward the optimal structure of the fronthaul compression and CP decoding strategies for the compress-and-forward scheme in C-RAN. On the CP decoding strategy design, this paper shows that under a sum fronthaul capacity constraint, a generalized successive decoding strategy of the quantization and user message codewords that allows arbitrary interleaved order at the CP achieves the same rate region as the optimal joint decoding. Further, it is shown that a practical strategy of successively decoding the quantization codewords first, then the user messages, achieves the same maximum sum rate as joint decoding under individual fronthaul constraints. On the joint optimization of user transmission and BS quantization strategies, this paper shows that if the input distributions are assumed to be Gaussian, then under joint decoding, the optimal quantization scheme for maximizing the achievable rate region is Gaussian. Moreover, Gaussian input and Gaussian quantization with joint decoding achieve to within a constant gap of the capacity region of the Gaussian multipleinput multiple-output (MIMO) uplink C-RAN model. Finally, this paper addresses the computational aspect of optimizing uplink MIMO C-RAN by showing that under fixed Gaussian input, the sum rate maximization problem over the Gaussian quantization noise covariance matrices can be formulated as convex optimization problems, thereby facilitating its efficient solution. Index Terms-Cloud radio access network, multiple-access relay channel, compress-and-forward, fronthaul compression, joint decoding, generalized successive decoding. (C-RAN) is an emerging mobile network architecture in which base-stations (BSs) in multiple cells are connected to a cloud-computing based central processor (CP) through wired/wireless fronthaul links. In the deployment of a C-RAN system, the BSs degenerate into remote antennas heads implementing only radio functionalities, such as frequency up/down conversion, sampling, filtering, and power amplification. The baseband operations at the BSs are migrated to the CP. The C-RAN model effectively virtualizes radio-access operations such as the encoding and decoding of user information and the optimization of radio resources [1]. Advanced joint multicell processing techniques, such as the coordinated multi-point (CoMP) and network multiple-input multiple-output (MIMO), can be efficiently supported by the C-RAN architecture, potentially enabling significantly higher data rates than conventional cellular networks [2]. This paper considers the uplink of a MIMO C-RAN system under finite...

A simple, mild and green route is developed for the preparation of uniform polystyrene-methyl acrylic acid/ silver (PSMAA/Ag) nanocomposite spheres with high catalytic activities. In this approach, monodisperse polystyrene-methyl acrylic acid (PSMAA) spheres are used as polymeric matrixes; silver precursor-[Ag(NH 3 ) 2 ] + ions are then adsorbed onto the surfaces of PSMAA spheres due to the strong electrostatic attraction between carboxyl groups (electronegative) and [Ag(NH 3 ) 2 ] + ions (electropositive). Meanwhile, [Ag(NH 3 ) 2 ] + ions are reduced to Ag nanoparticles and simultaneously protected by PVP on the surface of PSMAA spheres. In this way, the PSMAA/Ag nanocomposite spheres with loading Ag nanoparticles on PSMAA spheres are prepared in aqueous media without any toxic reagents used during the preparation process. Ag nanoparticles uniformly distribute on the surfaces of PSMAA spheres with its size ranging from 8 to 24 nm. Moreover, the coverage degree of Ag nanoparticles on PSMAA spheres increases with the increasing of concentration of silver precursor-[Ag(NH 3 ) 2 ] + ions. In addition, thermal analysis results show that the prepared PSMAA/Ag nanocomposite spheres exhibit improved thermal stabilities and glass translation temperature when compared to the related neat PSMAA spheres. Catalytic studies indicate that the prepared PSMAA/Ag nanocomposite spheres exhibit high catalytic activities and good recyclability for the reduction of 4-nitrophenol, rendering a potential use in the fields of catalytic reduction of 4-nitrophenol to 4-aminophenol.

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Molecular dynamics simulation was used to examine the growth of methane hydrate in the presence of natural product pectin at different concentrations, including the mass fractions 2.46% and 3.62%. Snapshots of the system configurations with time, radial distribution functions of the carbon atoms, and the total energy of the system were employed to characterize the effect of pectin on methane hydrate growth. Results indicated that pectin is a good inhibitor of methane hydrate. The higher the concentration of pectin is, the better the effect of inhibition is. The double-bonded oxygen atoms of pectin combine with hydrogen atoms of water, and the hydrogen atoms of hydroxyl in pectin combine with oxygen atoms of water through hydrogen bonds, which disturbed the further growth of the methane hydrate. The role of the pectin’s active groups in hydrogen bonds with water both as proton donor and as electron acceptor makes pectin have a better inhibitory effect on the growth of methane hydrate.